1. Field
The present disclosure relates to artificial skin or electronic skin. The present disclosure relates to conductive hydrogel.
2. Description of the Related Art
Biological skin has the ability to sense external stimulations, the ability to repeatedly heal injuries, and flexibility to adapt to motions of muscles. Research is being conducted from various vantage points to obtain artificial skin that imitates such biological skin.
Requirements of the artificial skin include the following four requirements: first, in terms of mechanical property, “flexibility” to adapt to motions of muscles is required. Flexibility may be measured by Young's modulus. Second, in terms of functionality, “electrical conductivity” is needed to transmit electrical signals generated from external stimulations. Third, “healing property” is required. Healing property refers to the ability to repeat an injury-healing cycle many times. Fourth, in terms of a biological property, “biocompatibility” is required. Biocompatibility refers to bio-friendliness (i.e., the quality of not having toxic or injurious effects on biological systems) of materials used in the artificial skin.
An example of conventional artificial skin is a flexible substrate with an electronic device (for example, a capacitor or a transistor) embedded on the flexible substrate. See, “Nature Mater. (2010), 9, 859, Stanford”; “Nature Mater. (2010), 9, 821, Berkeley,” and “Nature Nanotech. (2011), 6, 788, Stanford.” However, in this case, although the requirements of mechanical property and functionality are satisfied, the requirements of healing property and biocompatibility are not satisfied.
Other example of the artificial skin is hydrogel or a synthetic polymer having healing properties. See, “Science (2002), 295, 1698, UCLA & USC,” “PNAS (2012), 109, 4383, UCSD,” and “Nature Comm (2011), 2, 1, Osaka.”. However, in this case, the requirements of healing property and biocompatibility may be satisfied, but the requirements of mechanical property and functionality are not satisfied.
Another example of the conventional artificial skin is a material that may self-heal injured portions to recover electrical properties. See, “Nature Nanotech (2012), Online, Stanford”; and “Adv. Mater. (2012), 24, 2578.” However, in this case, the requirements of mechanical property, functionality, and healing property may be satisfied, but the requirement of biocompatibility is not satisfied.
Another example of the conventional artificial skin is obtained by directly embedding various sensors onto biological skin. See, “PNAS (2011), Harvard” and “Science (2011), 333, 830, URIC.” However, in this case, the requirements of mechanical property and functionality may be satisfied, but the requirements of healing property and biocompatibility are not satisfied.
Accordingly, conventional artificial skin candidates only satisfy one to three requirements of the four requirements of artificial skin.